Voters in Croatia on Sunday will choose a new president who is expected to lead the Balkan nation into the European Union. The race is between a leftist intellectual who has pledged to fight high-level corruption and the populist mayor of Zagreb.

Croats have begun voting in the decisive round of presidential elections with opinion polls predicting a narrow victory for left-leaning candidate Ivo Josipovic.

The 52-year-old bespectacled law professor and classical music composer, who is backed by the main opposition Social Democrats, won the first election round on December 27, with about one-third of the vote.

Josipovic has told Croatian television that he wants a return of integrity into politics amid international concerns over financial wrongdoing in Croatia.

He pledges to tackle corruption and organized crime. Croatia has in his words to re-establish public trust in law enforcement institutions such as police, the courts and politics. Josipovic also wants to improve the general living conditions of people.

Josipovic's challenger is the controversial mayor of Zagreb, Milan Bandic, a former Social Democrat who has been criticized for populist policies.

Local media accuse Bandic and the city administration he controls of links
to corruption scandals.

But Bandic has said no charges were ever pressed against him.

He recently received backing from the influential Catholic Church and is popular among 400,000 Croatian voters living abroad, mostly in neighboring Bosnia-Herzegovina, where he was born.

Despite controversies, Mayor Bandic, who is 54, says he can be a good president, citing his experience as major of Croatia's capital.

Mayor Bandic tells Croatian television that while being mayor of Zagreb in the last 10 years he did much to promote Croatia. He adds he did everything to "promote Zagreb as a European metropolis." Bandic favors European Union membership for Croatia. He describes the EU as an organization with high social standards and prosperity which could help provide a better future for his Balkan nation.

Both presidential candidates support Croatia's aim to join the EU next year or in 2012. But European diplomats say Ivo Josipovic is more likely to support the government's new anti-corruption efforts, a key condition for membership.

Any new president can also expect Western pressure to mend relations with
neighboring Serbia, another EU candidate country. Serbia is furious that outgoing Croatian President Stipe Mesic on Friday visited Kosovo, which declared independence but is viewed as a Serbian province by Belgrade.

Additionally Serbia has filed a lawsuit this week at the World Court accusing Croatia of genocide against Serbs during their Balkan war of the 1990s. It was a response to a similar one that Croatia filed against Serbia over a decade ago.

The war began after Croatia declared itself independent from what was Yugoslavia in 1991. It is not yet clear which steps Croatia's next president can take to improve relations with its neighbor.

First official results of Sunday's presidential poll are expected by early Monday. Nearly four-and-a-half million people can participate in the voting.